This disclosure relates to polycarbonate and methods of making polycarbonate, particularly polycarbonate having a low level of ionic species and residual monomers.
Polycarbonate, a thermoplastic that has excellent impact resistance and other mechanical properties, as well as heat resistance and transparency, is widely used in many engineering applications, including mechanical parts, optical disks, and automotive parts.
Polycarbonates may be produced by an interfacial method employing phosgene, a melt process employing phosgene and a melt process that does not employ phosgene. Regardless of the synthetic method it is desirable for the polycarbonate to have a low level of ionic species (cations and anions), unreacted monomers and small molecule side products. Ionic species can affect the quality of the polycarbonate, particularly with regard to color, molecular weight, rheological and/or electrical properties. Unreacted monomers and small molecule side products can result in outgassing and the dirtying of injector molds and extruder dies. Outgassing is particularly undesirable in electronic devices and components where the released gas can have a negative impact on surrounding components and materials. In addition unreacted monomers and small molecule side products can be detrimental to the taste and other organoleptic properties of food and beverages residing in containers made of polycarbonate.
Therefore, a need exists for method of preparing a polycarbonate that has low levels of ionic species, unreacted monomers and small molecule side products.